The invention relates to a traction roller transmission with fixed transmission ratio, particularly to a planetary-type traction roller transmission.
Such a transmission includes a traction ring having disposed therein a sun roller and planetary rollers arranged in the annular space between and in engagement with, the sun roller and the traction ring for the transmission of motion between the sun roller and the traction ring. As disclosed in the present inventor's earlier U.S. Pat. No. 3,776,051, the sun roller may be so arranged that its axis is parallel to, but spaced from, the axis of the traction ring such that the annular space between the sun roller and the traction ring is of varying width and the traction rollers are so arranged that at least one of them is pulled by the reaction forces into a narrowing section of the annular space when a torque is transmitted, thereby causing firm engagement of the traction rollers with the traction ring and the sun roller.
However, if the traction roller axes are not perfectly parallel with the axis of the sun roller and the traction ring, large axial forces are generated which cause large axial bearing loads on all transmission bearings. In the arrangement according to the present inventor's earlier U.S. Pat. No. 3,941,004, the traction ring has annular guide rails provided with guide surfaces which are disposed adjacent the side faces of the traction rollers in closely spaced relationship such that, during operation of the transmission, lubricant present in the transmission and adhering to the guide surfaces and annular side faces is drawn into the gaps therebetween and forms therein pressurized lubricant pads which steer the traction rollers into parallel alignment with the traction ring.
It has been found however, that, during high speed operation, the lubricant shear losses in said gaps become relatively large. Furthermore, it has been found that particulate matter entering the narrow gap causes wear of the guide surfaces.